foreach $phrase (@key_phrases) {
     my($worda,$wordb) = split(/ /, $phrase);
     my $pattern = qr/(\W|\b)($worda)(\W+)($wordb)(\W|\b)/;
     foreach (@material) {
          last if (s,$pattern,$1<U>$2</U>$3<U>$4</U>$5,i);
     }
}